We present an extension of discrete relative time process algebra
where recursion, propositional signals, a counting process creation
operator and the state operator are combined.  A semantics of
$\varphi\!\!^-$SDL, a small subset of SDL that is closely connected
with full SDL, is proposed which describes the meaning of
$\varphi\!\!^-$SDL constructs using this extension.  This semantics
allows for the generation of finitely branching transition systems for
$\varphi\!\!^-$SDL specifications.